This invention relates generally to computer systems, and more particularly to a mechanism for enabling a customized session manager to interact with a network server.
On the Internet or World Wide Web, information is generally communicated on a request-response basis. That is, a client (typically running a browser program) submits a service request to a server. The service request may simply ask for a static page (usually in HTML format), or it may request that a particular application or program be executed to generate a return page. In response to the service request, the server performs whatever tasks are necessary to service the request, and provides a return page to the client. This request-response sequence, referred to as a “roundtrip”, is carried out for each request.
Generally, the Internet is a stateless environment. That is, each service request is treated as its own individual request, and there is no “memory” of prior requests. Put another way, the server makes no association between a current request and a previous request, even if the requests are from the same client, and even if the requests have some common nexus. For simple applications in which every task that needs to be performed can be carried out in a single roundtrip, this statelessness is not a problem. However, for exchanges (such as transactions) that require multiple roundtrips, the lack of state presents a significant impediment.
An example of an application in which it is necessary to maintain state across multiple roundtrips is that of an “electronic shopping cart” application. More specifically, a user visits a merchant's website using a particular client machine. As the user peruses the website, he sees an item that he wishes to purchase, and puts that item into his “shopping cart”. As some point, the user invokes a link to another page of the website, and at that point, a request is sent to the server which requests the desired page and which also provides to the server all of the items currently in the shopping cart. The server responds to the request by storing information pertaining to the shopping cart items, and by providing the desired page to the client. Thereafter, the user peruses the new page and puts additional items into the shopping cart. In a subsequent request by the client, the additional items in the shopping are sent to the server. Since the subsequent request is from the same client, the server should associate the additional items with the previous items as being in the same shopping cart. To do this, though, the server needs to associate the subsequent request with the previous request, which in turn requires that the server maintain state information relating to the requests. However, as noted above, the Internet is generally a stateless environment. As a result, without further functionality on the part of the server, multiple roundtrip exchanges, such as those required by the electronic shopping cart application, cannot be implemented on the Internet.
To enable exchanges which require multiple roundtrips, some servers implement a session management functionality. Basically, this functionality maintains state information across multiple roundtrips so that associations between multiple requests can be made. Usually, state information is maintained by passing session ID information back and forth between the client and the server. For example, when a service on the server requiring state information is first invoked by a client request, a new session is created, and a new session ID is associated with the new session. The session acts as a “container” that can be used to store all of the necessary state information relating to that particular session. Once the session is created (and possibly updated to include state information relating to processing of the current request), the associated session ID is provided to the client that requested the service. If that client makes a subsequent request to the same service, the client includes in that request the session ID. Using the session ID, the server accesses the associated session, and based upon the state information stored in the associated session, the server can determine what has transpired thus far. In this manner, the server is able to associate a current request with one or more previous requests.
Typically, the session management functionality of a server is an integral part of the server. This means that in order to make any changes to the session management functionality, it is necessary to change and to recompile the core server code. While this simplifies the overall architecture of the server, it can lead to significant drawbacks, such as inflexibility and non-scalability. Both of these limit the overall effectiveness of the server. As a result, there is a need for an improved session management architecture.